This invention relates to a light source device, particularly adapted for use in an endoscope used to illuminate the interior of a body cavity.
As is well known, in an endoscope the interior of a body cavity is examined by means of light from a light source passing through a fiber optical system towards the end of said endoscope. As a result it is possible to effect peep-through observation or photography. Often there is provided separate light sources for simple viewing and for photography, respectively. The first being a conventional light source and the latter being a flash light source.
Visual examination of a mucus membrane part to be examined within a body cavity using an endoscope is carried out under the illumination thereof by a conventional lamp such as a tungsten filament lamp, having a relatively low intensity of illumination because of the possibility of damage to the membrane by sustained high intensity light. It is also typical to photograph the desired part after it has been found by simple viewing and adjustment of the endoscope tip. Photographic recording is carried out under the instantaneous illumination at a high intensity by using a xenon discharge tube or the like. Accordingly, the endoscope illumination device must include an observing light source and a photographic light source.
The latter light sources are provided external to the fiber optical system of the endoscope. The fiber optical system usually comprises a small-diameter introducing portion, for entry of an objective lens into a part of the body to be examined, and an operating portion with an eyepiece arranged thereon. However, since the introducing portion is required to be flexible and to have a very small diameter the fiber bundles for transmitting light from the lamps to the object and the fiber bundles for transmitting the image light from the object to the eyepiece must necessarily be constrained so as to permit only a single light path or guide. Therefore, both the conventional light and the photography light must impinge the same entry port of the light guide.
Generally, the light sources are arranged such that a flash discharge tube is arranged in front of a tungsten filament lamp which has a reflector at the back thereof. The disposition of the two lamps is such that the discharge lamp would block a substantial amount of the light from the conventional lamp from entering the light guide, were it not for complicated lens systems or specially designed arrangements typically provided to ameliorate the problem. Such systems and arrangements are not satisfactory because of their complexity.